Formation of a tantalum-nitride layer

ABSTRACT

A method of forming a material on a substrate is disclosed. In one embodiment, the method includes forming a tantalum nitride layer on a substrate disposed in a plasma process chamber by sequentially exposing the substrate to a tantalum precursor and a nitrogen precursor, followed by reducing a nitrogen concentration of the tantalum nitride layer by exposing the substrate to a plasma annealing process. A metal-containing layer is subsequently deposited on the tantalum nitride layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 12/846,253, filed Jul.29, 2010 now U.S. Pat. No. 8,114,789, which is a continuation of U.S.Ser. No. 11/240,189, filed Sep. 30, 2005 now U.S. Pat. No. 7,781,326,which is a continuation of Ser. No. 11/088,072, filed Mar. 23, 2005, nowU.S. Pat. No. 7,094,680, which is a continuation of U.S. Ser. No.09/776,329, filed Feb. 2, 2001, now U.S. Pat. No. 6,951,804, all ofwhich are hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to formation of one or more barrier layersand, more particularly, to one or more barrier layers formed usingchemisorption techniques.

2. Description of the Related Art

In manufacturing integrated circuits, one or more barrier layers areoften used to inhibit diffusion of one or more materials in metallayers, as well as other impurities from intermediate dielectric layers,into elements underlying such barrier layers, such as transistor gates,capacitor dielectrics, transistor wells, transistor channels, electricalbarrier regions, interconnects, among other known elements of integratedcircuits.

Though a barrier layer may limit to prevent migration of unwantedmaterials into such elements, its introduction creates an interface atleast in part between itself and one or more metal layers. For subhalf-micron (0.5 μm) semiconductor devices, microscopic reaction at aninterface between metal and barrier layers can cause degradation ofintegrated circuits, including but not limited to increased electricalresistance of such metal layers. Accordingly, though barrier layers havebecome a component for improving reliability of interconnectmetallization schemes, it is desirable to mitigate “side effects” causedby introduction of such barrier layers.

Compounds of refractory metals such as, for example, nitrides, borides,and carbides are targets as diffusion barriers because of their chemicalinertness and low resistivities (e.g., sheet resistivities typicallyless than about 200 μΩ-cm). In particular, borides such as, includingbut not limited to titanium diboride (TiB₂), have been used as a barriermaterial owing to their low sheet resistivities (e.g., resistivitiesless than about 150 μΩ-cm).

Boride barrier layers are conventionally formed using chemical vapordeposition (CVD) techniques. For example, titanium tetrachloride (TiCl₄)may be reacted with diborane (B₂H₆) to form titanium diboride (TiB₂)using CVD. However, when Cl-based chemistries are used to form boridebarrier layers, reliability problems can occur. In particular, boridelayers formed using CVD chlorine-based chemistries typically have arelatively high chlorine (Cl) content, namely, chlorine content greaterthan about 3 percent. A high chlorine content is undesirable becausemigrating chlorine from a boride barrier layer into adjacentinterconnection layer may increase contact resistance of suchinterconnection layer and potentially change one or more characteristicsof integrated circuits made therewith.

Therefore, a need exists for barrier layers for integrated circuitfabrication with little to no side effects owing to their introduction.Particularly desirable would be a barrier layer useful for interconnectstructures.

SUMMARY OF THE INVENTION

An aspect of the present invention is film deposition for integratedcircuit fabrication. More particularly, at least one element from afirst precursor and at least one element from a second precursor ischemisorbed on a surface. The at least one element from the firstprecursor and the at least one element from the second precursor arechemisorbed to provide a tantalum-nitride film. This sequence may berepeated to increase tantalum-nitride layer thickness. This type ofdeposition process is sometimes called atomic layer deposition (ALD).Such a tantalum-nitride layer may be used as a barrier layer.

Another aspect is forming the tantalum-nitride layer using in partannealing of at least one tantalum-nitride sublayer. This annealing maybe done with a plasma.

Another aspect is using a plasma source gas as a nitrogen precursor. Theplasma source gas may be used to provide a plasma, which may besequentially reacted or co-reacted with a tantalum containing precursor.

In another aspect, a method of film deposition for integrated circuitfabrication includes forming a tantalum nitride layer by sequentiallychemisorbing a tantalum precursor and a nitrogen precursor on asubstrate disposed in a process chamber. A nitrogen concentration of thetantalum nitride layer is reduced by exposing the substrate to a plasmaannealing process. A metal-containing layer is subsequently deposited onthe tantalum nitride layer.

In another aspect, a method of film deposition for integrated circuitfabrication includes forming a tantalum nitride layer with a firstnitrogen concentration on a substrate by an atomic layer depositionprocess. An upper portion of the tantalum nitride layer is exposed to aplasma annealing process to form a tantalum-containing layer with asecond nitrogen concentration. A metal-containing layer is thendeposited on the tantalum-containing layer.

In another aspect, a method of film deposition for integrated circuitfabrication includes forming a tantalum-containing layer with a sheetresistance of about 1,200 μΩ-cm or less by a plasma annealing process ona tantalum nitride layer deposited by an atomic layer deposition processon a substrate.

In yet another aspect, a method of forming a material on a substrate isdisclosed. In one embodiment, the method includes forming a tantalumnitride layer on a substrate disposed in a plasma process chamber bysequentially exposing the substrate to a tantalum precursor and anitrogen precursor, followed by reducing a nitrogen concentration of thetantalum nitride layer by exposing the substrate to a plasma annealingprocess. A metal-containing layer is then deposited on the tantalumnitride layer by a deposition process.

These and other aspects of the present invention will be more apparentfrom the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIGS. 1 and 4 depict schematic illustrations of exemplary portions ofprocess systems in accordance with one or more integrated circuitfabrication aspects of the present invention;

FIGS. 2 a-2 c depict cross-sectional views of a substrate structure atdifferent stages of integrated circuit fabrication;

FIGS. 3 a-3 c depict cross-sectional views of a substrate at differentstages of chemisorption to form a barrier layer; and

FIG. 5 depicts a cross-sectional view of a substrate structure atdifferent stages of integrated circuit fabrication incorporating one ormore tantalum-nitride barrier sublayers post plasma anneal.

DETAILED DESCRIPTION

FIG. 1 depicts a schematic illustration of a wafer processing system 10that can be used to form one or more tantalum-nitride barrier layers inaccordance with aspects of the present invention described herein.System 10 comprises process chamber 100, gas panel 130, control unit110, along with other hardware components such as power supply 106 andvacuum pump 102. For purposes of clarity, salient features of processchamber 100 are briefly described below.

Process Chamber

Process chamber 100 generally houses a support pedestal 150, which isused to support a substrate such as a semiconductor wafer 190 withinprocess chamber 100. Depending on process requirements, semiconductorwafer 190 can be heated to some desired temperature or within somedesired temperature range prior to layer formation using heater 170.

In chamber 100, wafer support pedestal 150 is heated by an embeddedheating element 170. For example, pedestal 150 may be resistively heatedby applying an electric current from an AC power supply 106 to heatingelement 170. Wafer 190 is, in turn, heated by pedestal 150, and may bemaintained within a desired process temperature range of, for example,about 20 degrees Celsius to about 500 degrees Celsius.

Temperature sensor 172, such as a thermocouple, may be embedded in wafersupport pedestal 150 to monitor the pedestal temperature of 150 in aconventional manner. For example, measured temperature may be used in afeedback loop to control electric current applied to heating element 170from power supply 106, such that wafer temperature can be maintained orcontrolled at a desired temperature or within a desired temperaturerange suitable for a process application. Pedestal 150 may optionally beheated using radiant heat (not shown).

Vacuum pump 102 is used to evacuate process gases from process chamber100 and to help maintain a desired pressure or desired pressure within apressure range inside chamber 100. Orifice 120 through a wall of chamber100 is used to introduce process gases into process chamber 100. Sizingof orifice 120 conventionally depends on the size of process chamber100.

Orifice 120 is coupled to gas panel 130 in part by valve 125. Gas panel130 is configured to receive and then provide a resultant process gasfrom two or more gas sources 135, 136 to process chamber 100 throughorifice 120 and valve 125. Gas sources 135, 136 may store precursors ina liquid phase at room temperature, which are later heated when in gaspanel 130 to convert them to a vapor-gas phase for introduction intochamber 100. Gas panel 130 is further configured to receive and thenprovide a purge gas from purge gas source 138 to process chamber 100through orifice 120 and valve 125.

Control unit 110, such as a programmed personal computer, work stationcomputer, and the like, is configured to control flow of various processgases through gas panel 130 as well as valve 125 during different stagesof a wafer process sequence. Illustratively, control unit 110 comprisescentral processing unit (CPU) 112, support circuitry 114, and memory 116containing associated control software 113. In addition to control ofprocess gases through gas panel 130, control unit 110 may be configuredto be responsible for automated control of other activities used inwafer processing—such as wafer transport, temperature control, chamberevacuation, among other activities, some of which are describedelsewhere herein.

Control unit 110 may be one of any form of general purpose computerprocessor that can be used in an industrial setting for controllingvarious chambers and sub-processors. CPU 112 may use any suitable memory116, such as random access memory, read only memory, floppy disk drive,hard disk, or any other form of digital storage, local or remote.Various support circuits may be coupled to CPU 112 for supporting system10. Software routines 113 as required may be stored in memory 116 orexecuted by a second computer processor that is remotely located (notshown). Bi-directional communications between control unit 110 andvarious other components of wafer processing system 10 are handledthrough numerous signal cables collectively referred to as signal buses118, some of which are illustrated in FIG. 1.

Barrier Layer Formation

FIGS. 2 a-2 c illustrate exemplary embodiment portions oftantalum-nitride layer formation for integrated circuit fabrication ofan interconnect structure in accordance with one or more aspects of thepresent invention. For purposes of clarity, substrate 200 refers to anyworkpiece upon which film processing is performed, and substratestructure 250 is used to denote substrate 200 as well as other materiallayers formed on substrate 200. Depending on processing stage, substrate200 may be a silicon semiconductor wafer, or other material layer, whichhas been formed on wafer 190 (shown in FIG. 1).

FIG. 2 a, for example, shows a cross-sectional view of a substratestructure 250, having a dielectric layer 202 thereon. Dielectric layer202 may be an oxide, a silicon oxide, carbon-silicon-oxide, afluoro-silicon, a porous dielectric, or other suitable dielectric formedand patterned to provide contact hole or via 202H extending to anexposed surface portion 202T of substrate 200. More particularly, itwill be understood by those with skill in the art that the presentinvention may be used in a dual damascene process flow.

FIG. 2 b illustratively shows tantalum-nitride layer 204 formed onsubstrate structure 250. Tantalum-nitride layer 204 is formed bychemisorbing monolayers of a tantalum containing compound and a nitrogencontaining compound on substrate structure 250.

Referring to FIG. 2 c, after the formation of tantalum-nitride layer204, a portion of layer 204 may be removed by etching in a well-knownmanner to expose a portion 202C of substrate 200. Portion 202C may bepart of a transistor gate stack, a capacitor plate, a node, a conductor,or like conductive element. Next, contact layer 206 may be formedthereon, for example, to form an interconnect structure. Contact layer206 may be selected from a group of aluminum (Al), copper (Cu), tungsten(W), and combinations thereof.

Contact layer 206 may be formed, for example, using chemical vapordeposition (CVD), physical vapor deposition (PVD), electroplating, or acombination thereof. For example, an aluminum (Al) layer may bedeposited from a reaction of a gas mixture containing dimethyl aluminumhydride (DMAH) and hydrogen (H₂) or argon (Ar) or other DMAH containingmixtures, a CVD copper layer may be deposited from a gas mixturecontaining Cu(hfac)₂ (copper (II) hexafluoro acetylacetonate), Cu(fod)₂(copper (II) heptafluoro dimethyl octanediene), Cu(hfac) TMVS (copper(I) hexafluoro acetylacetonate trimethylvinylsilane) or combinationsthereof, and a CVD tungsten layer may be deposited from a gas mixturecontaining tungsten hexafluoride (WF₆). A PVD layer is deposited from acopper target, an aluminum target, or a tungsten target.

Moreover, layer 206 may be a refractory metal compound including but notlimited to titanium (Ti), tungsten (W), tantalum (Ta), zirconium (Zr),hafnium (Hf), molybdenum (Mo), niobium (Nb), vanadium (V), and chromium(Cr), among others. Conventionally, a refractory metal is combined withreactive species, such as for example chlorine (Cl) or fluorine (F), andis provided with another gas to form a refractory metal compound. Forexample, titanium tetrachloride (TiCl₄), tungsten hexafluoride (WF₆),tantalum pentachloride (TaCl₅), zirconium tetrachloride (ZrCl₄), hafniumtetrachloride (HfCl₄), molybdenum pentachloride (MoCl₅), niobiumpentachloride (NbCl₅), vanadium pentachloride (VCl₅), or chromiumtetrachloride (CrCl₄) may be used as a refractory metal-containingcompound gas.

Though layer 206 is shown as formed on layer 204, it should beunderstood that layer 204 may be used in combination with one or moreother barrier layers formed by CVD or PVD. Accordingly, layer 204 neednot be in direct contact with layer 206, but an intervening layer mayexist between layer 206 and layer 204.

Monolayers are chemisorbed by sequentially providing a tantalumcontaining compound and a nitrogen containing compound to a processchamber. Monolayers of a tantalum containing compound and a nitrogencontaining compound are alternately chemisorbed on a substrate 300 asillustratively shown in FIGS. 3 a-3 c.

FIG. 3 a depicts a cross-sectional view of an exemplary portion ofsubstrate 300 in a stage of integrated circuit fabrication, and moreparticularly at a stage of barrier layer formation. Tantalum layer 305is formed by chemisorbing a tantalum-containing compound on surfaceportion 300T of substrate 300 by introducing a pulse of a tantalumcontaining gas 135 (shown in FIG. 1) into process chamber 100 (shown inFIG. 1). Tantalum containing gas 135 (shown in FIG. 1) may be a tantalumbased organometallic precursor or a derivative thereof. Examples of suchprecursors include but are not limited to pentakis(ethylmethylamino)tantalum (PEMAT; Ta(N(Et)Me)₅), pentakis(diethylannino) tantalum (PDEAT;Ta(NEt₂)₅), pentakis(dimethylamino) tantalum (PDMAT; Ta(NMe₂)₅) or aderivative thereof. Other tantalum containing precursors include TBTDET(^(t)BuNTa(NEt₂)₃ or C₁₆H₃₉N₄Ta), tantalum halides (e.g., TaX₅, where Xis F, B or C) or a derivative thereof.

Wafer 190 is maintained approximately below a thermal decompositiontemperature of a selected tantalum precursor or a derivative thereof tobe used and maintained at a pressure of approximately less than 100Torr. Additionally, wafer 190 may be heated by heating element 170. Anexemplary temperature range for precursors identified herein isapproximately 20 to 400 degrees Celsius. For example, approximately 150to 300 degrees Celsius may be used for PEMAT.

Though temperatures below a thermal decomposition temperature may beused, it should be understood that other temperatures, namely thoseabove a thermal decomposition temperature, may be used. An exampletemperature ranges above a thermal decomposition temperature isapproximately 400 to 600 degrees Celsius. Accordingly, some thermaldecomposition may occur; however, the main, more than 50 percent,deposition activity is by chemisorption. More generally, wafer surfacetemperature needs to be high enough to induce significant chemisorptionof precursors instead of physisorption, but low enough to preventsignificant decomposition of precursors. If the amount of decompositionduring each precursor deposition is significantly less than a layer,then the primary growth mode will be ALD. Accordingly, such a film willtend to have ALD properties. However, it is possible if a precursorsignificantly decomposes, but an intermediate reactant is obtainedpreventing further precursor decomposition after a layer of intermediatereactant is deposited, then an ALD growth mode may still be obtained.

While not wishing to be bound by theory, it is believed that thistantalum-containing precursor combines tantalum atoms with one or morereactive species. During tantalum layer 305 formation, these reactivespecies form byproducts that are transported from process chamber 100 byvacuum system 102 while leaving tantalum deposited on surface portion300T. However, composition and structure of precursors on a surfaceduring atomic-layer deposition (ALD) is not precisely known. A precursormay be in an intermediate state when on a surface of wafer 190. Forexample, each layer may contain more than simply elements of tantalum(Ta) or nitrogen (N); rather, the existence of more complex moleculeshaving carbon (C), hydrogen (H), and/or oxygen (O) is probable.Additionally, a surface may saturate after exposure to a precursorforming a layer having more or less than a monolayer of either tantalum(Ta) or nitrogen (N). This composition or structure will depend onavailable free energy on a surface of wafer 190, as well as atoms ormolecules involved. Once all available sites are occupied by tantalumatoms, further chemisorption of tantalum is blocked, and thus thereaction is self-limiting.

After layer 305 of a tantalum containing compound is chemisorbed ontosubstrate 300, excess tantalum containing compound is removed fromprocess chamber 10 by vacuum system 102 (shown in FIG. 1). Additionally,a pulse of purge gas 138 (shown in FIG. 1) may be supplied to processchamber 10 to facilitate removal of excess tantalum containing compound.Examples of suitable purge gases include but are not limited to helium(He), nitrogen (N₂), argon (Ar), and hydrogen (H₂), among others, andcombinations thereof that may be used.

With continuing reference to FIGS. 3 a-c and renewed reference to FIG.1, after process chamber 100 has been purged, a pulse of ammonia gas(NH₃) 136 is introduced into process chamber 100. Process chamber 100and wafer 190 may be maintained at approximately the same temperatureand pressure range as used for formation of layer 305.

In FIG. 3 b, a layer 307 of nitrogen is illustratively shown aschemisorbed on tantalum layer 305 at least in part in response tointroduction of ammonia gas 136. While not wishing to be bound bytheory, it is believed that nitrogen layer 307 is formed in a similarself-limiting manner as was tantalum layer 305. Each tantalum layer 305and nitrogen layer 307 in any combination and in direct contact with oneanother form a sublayer 309, whether or not either or both or neither isa monolayer. Though ammonia gas is used, other N containing precursorsgases may be used including but not limited to N_(x)H_(y) for x and yintegers (e.g., N₂H₄), N₂ plasma source, NH₂N(CH₃)₂, among others.

After an ammonia gas compound is chemisorbed onto tantalum layer 305 onsubstrate 300 to form nitrogen monolayer 307, excess ammonia gascompound is removed from process chamber 10 by vacuum system 102, andadditionally, a pulse of purge gas 138 may be supplied to processchamber 10 to facilitate this removal.

Thereafter, as shown in FIG. 3 c, tantalum and nitrogen layer depositionin an alternating sequence may be repeated with interspersed purgesuntil a desired layer 204 thickness is achieved. Tantalum-nitride layer204 may, for example, have a thickness in a range of approximately0.0002 microns (2 Angstrom) to about 0.05 microns (500 Angstrom), thougha thickness of approximately 0.001 microns (10 Angstrom) to about 0.005microns (50 Angstrom) may be a sufficient barrier. Moreover, atantalum-nitride layer 204 may be used as a thin film insulator ordielectric, or may be used as a protective layer for example to preventcorrosion owing to layer 204 being relatively inert or non-reactive.Advantageously, layer 204 may be used to coat any of a variety ofgeometries.

In FIGS. 3 a-3 c, tantalum-nitride layer 204 formation is depicted asstarting with chemisorption of a tantalum containing compound onsubstrate 300 followed by chemisorption of a nitrogen containingcompound. Alternatively, chemisorption may begin with a layer of anitrogen containing compound on substrate 300 followed by a layer of atantalum containing compound.

Pulse time for each pulse of a tantalum containing compound, a nitrogencontaining compound, and a purge gas is variable and depends on volumecapacity of a deposition chamber 100 employed as well as vacuum system102 coupled thereto. Similarly, time between each pulse is also variableand depends on volume capacity of process chamber 100 as well as vacuumsystem 102 coupled thereto. However, in general, wafer 190 surface mustbe saturated by the end of a pulse time, where pulse time is defined astime a surface is exposed to a precursor. There is some variabilityhere, for example (1) a lower chamber pressure of a precursor willrequire a longer pulse time; (2) a lower precursor gas flow rate willrequire a longer time for chamber pressure to rise and stabilizerequiring a longer pulse time; and (3) a large-volume chamber will takelonger to fill, longer for chamber pressure to stabilize thus requiringa longer pulse time. In general, precursor gases should not mix at ornear the wafer surface to prevent co-reaction (a co-reactive embodimentis disclosed elsewhere herein), and thus at least one gas purge or pumpevacuation between precursor pulses should be used to prevent mixing.

Generally, a pulse time of less than about 1 second for a tantalumcontaining compound and a pulse time of less than about 1 second for anitrogen containing compound is typically sufficient to chemisorbalternating monolayers that comprise tantalum-nitride layer 204 onsubstrate 300. A pulse time of less than about 1 second for purge gas138 is typically sufficient to remove reaction byproducts as well as anyresidual materials remaining in process chamber 100.

Sequential deposition as described advantageously provides good stepcoverage and conformality, due to using a chemisorption mechanism forforming tantalum-nitride layer 204. With complete or near completesaturation after each exposure of wafer 190 to a precursor, each ofuniformity and step coverage is approximately 100 percent. Becauseatomic layer deposition is used, precision controlled thickness oftantalum-nitride layer 204 may be achieved down to a single layer ofatoms. Furthermore, in ALD processes, since it is believed that onlyabout one atomic layer may be absorbed on a topographic surface per“cycle,” deposition area is largely independent of the amount ofprecursor gas remaining in a reaction chamber once a layer has beenformed. By “cycle,” it is meant a sequence of pulse gases, includingprecursor and purge gases, and optionally one or more pump evacuations.Also, by using ALD, gas-phase reactions between precursors are minimizedto reduce generation of unwanted particles.

Co-Reaction

Though it has been described to alternate tantalum and nitrogencontaining precursors and purging in between as applied in a sequentialmanner, another embodiment is to supply tantalum and nitrogen containingprecursors simultaneously. Thus, pulses of gases 135 and 136, namely,tantalum and nitrogen containing compounds, are both applied to chamber100 at the same time. An example is PEMAT and NH₃, though othertantalum-organic and nitrogen precursors may be used. Step coverage andconformality is good at approximately 95 to 100 percent for each.Moreover, deposition rate is approximately 0.001 to 0.1 microns persecond. Because a co-reaction is used, purging between sequential pulsesof alternating precursors is avoided, as is done in ALD.

Wafer surface temperature is maintained high enough to sustain reactionbetween two precursors. This temperature may be below chemisorptiontemperature of one or both precursors. Accordingly, temperature shouldbe high enough for sufficient diffusion of molecules or atoms.

Wafer surface temperature is maintained low enough to avoid significantdecomposition of precursors. However, more decomposition of precursorsmay be acceptable for co-reaction than for sequentially reactingprecursors in an ALD process. In general, wafer 190 surface diffusionrate of molecules or atoms should be greater than precursors' reactionrate which should be greater precursors' decomposition rate.

For all other details, the above-mentioned description for sequentiallyapplied precursors applies to co-reaction processing.

Plasma Anneal

After forming one or more combinations of layers 305 and 307, substratestructure 250 may be plasma annealed. Referring to FIG. 4, there isillustratively shown a schematic diagram of an exemplary portion of aprocess system 10P in accordance with an aspect of the presentinvention. Process system 10P is similar to process system 10, exceptfor additions of one or more RF power supplies 410 and 412, showerhead400, gas source 405, and matching network(s) 411. Notably, a separateplasma process system may be used; however, by using a CVD/PVD processsystem 10P, less handling of substrate structure 250 is involved, aslayer 204 may be formed and annealed in a same chamber 100.

Showerhead 400 and wafer support pedestal 150 provide in part spacedapart electrodes. An electric field may be generated between theseelectrodes to ignite a process gas introduced into chamber 100 toprovide a plasma 415. In this embodiment, argon is introduced intochamber 100 from gas source 405 to provide an argon plasma. However, ifargon is used as a purge gas, gas source 405 may be omitted for gassource 138.

Conventionally, pedestal 150 is coupled to a source of radio frequency(RF) power source 412 through a matching network 411, which in turn maybe coupled to control unit 110. Alternatively, RF power source 410 maybe coupled to showerhead 400 and matching network 411, which in turn maybe coupled to control unit 110. Moreover, matching network 411 maycomprise different circuits for RF power sources 410 and 412, and bothRF power sources 410 and 412 may be coupled to showerhead 400 andpedestal 150, respectively.

With continuing reference to FIG. 4 and renewed reference to FIG. 3 c,substrate structure 250 having one or more iterations ortantalum-nitride sublayers 309 is located in process chamber 401. Argon(Ar) gas from gas source 405 is introduced into chamber 401 to plasmaanneal substrate structure 250. While not wishing to be bound by theory,it is believed that plasma annealing reduces nitrogen content of one ormore sublayers 309 by sputtering off nitrogen, which in turn reducesresistivity. In other words, plasma annealing is believed to maketantalum-nitride layer 204 more tantalum-rich as compared to anon-plasma annealed tantalum-nitride layer 204. For example, a 1:1 Ta:Nfilm may be annealed to a 2:1 Ta:N film. Tantalum-nitride films having asheet resistance of approximately equal to or less than 1200microohms-cm for 0.004 micron (40 Angstrom) films may be achieved.

It will be appreciated that other non-chemically reactive gases withrespect to layer 204 may be used for physically displacing nitrogen fromlayer 204, including but not limited to neon (Ne), xenon (Xe), helium(He), and hydrogen (H₂). Generally, for a plasma-gas that does notchemically react with a tantalum-nitride film, it is desirable to have aplasma-gas atom or molecule with an atomic-mass closer to N than to Tain order to have preferential sputtering of the N. However, a chemicallyreactive process may be used where a gas is selected whichpreferentially reacts for removal of N while leaving Ta.

Referring to FIG. 5, there is illustratively shown a cross sectionalview of layer 204 after plasma annealing in accordance with a portion ofan exemplary embodiment of the present invention. Plasma annealing maybe done after formation of each nitrogen layer 307, or may be done afterformation of a plurality of layers 307. With respect to the latter,plasma annealing may take place after approximately every 0.003 to 0.005microns (30 to 50 Angstroms) of layer 204 or after formation ofapproximately every 7 to 10 sublayers 309. However, plasma annealing maybe done after formation of a sublayer 309, which is approximately 0.0001to 0.0004 microns (1 to 4 Angstroms).

Plasma annealing with argon may be done with a wafer temperature in arange of approximately 20 to 450 degrees Celsius and a chamber pressureof approximately 0.1 to 50 Torr with a flow rate of argon in a range ofapproximately 10 to 2,000 standard cubic centimeters per minute (sccm)with a plasma treatment time approximately equal to or greater than onesecond. Generally, a tantalum-nitride film should be annealed at atemperature, which does not melt, sublime, or decompose such atantalum-nitride film.

The specific process conditions disclosed in the above description aremeant for illustrative purposes only. Other combinations of processparameters such as precursor and inert gases, flow ranges, pressureranges and temperature ranges may be used in forming a tantalum-nitridelayer in accordance with one or more aspects of the present invention.

Although several preferred embodiments, which incorporate the teachingsof the present invention, have been shown and described in detail, thoseskilled in the art can readily devise many other varied embodiments thatstill incorporate these teachings. By way of example and not limitation,it will be apparent to those skilled in the art that the above-describedformation is directed at atomic layer CVD (ALCVD); however, lowtemperature CVD may be used as described with respect to co-reactingprecursors. Accordingly, layers 305 and 307 need not be monolayers.Moreover, it will be appreciated that the above described embodiments ofthe present invention will be particularly useful in forming one or morebarrier layers for interconnects on semiconductor devices having a widerange of applications.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

The invention claimed is:
 1. A method of forming a tantalum nitridefilm, comprising: (a) chemisorbing tantalum from a tantalum containingprecursor to form a layer of tantalum containing compound on asubstrate, wherein the substrate is maintained at a temperature between400 degrees Celsius to 600 degrees Celsius; (b) stopping the flow of thetantalum-containing precursor; (c) pulsing a purge gas to the substrateand stopping the flow of the purge Gas to provide a pulse time of lessthan about 1 second; (d) chemisorbing nitrogen from a nitrogencontaining precursor to a layer of nitrogen containing compound on thelayer of tantalum containing compound; (e) stopping the flow of thenitrogen containing precursor; (f) pulsing the purge gas to thesubstrate and stopping the flow of the purge gas to provide a pulse timeof less than about 1 second; and repeating (a)-(f) until a desiredthickness of the layers of tantalum containing compound and nitrogencontaining compound is reached.
 2. The method of claim 1, whereinchemisorbing tantalum from the tantalum containing precursor andchemisorbing nitrogen from the nitrogen containing precursor formsmultiple tantalum nitride sublayers on the substrate.
 3. The method ofclaim 1, further comprising: plasma annealing the layers of tantalumcontaining compound and nitrogen containing compound to remove nitrogentherefrom.
 4. The method of claim 3, wherein the plasma annealing isperformed with a plasma source material chemically non-reactive to thetantalum-nitride sublayers, the plasma source material having an atomicmass closer to nitrogen than tantalum.
 5. The method of claim 4, whereinthe plasma annealing is performed with plasma source material selectedfrom argon (Ar), xenon (Xe), helium (He), hydrogen (H₂), nitrogen (N₂),neon (Ne), and combinations thereof.
 6. The method of claim 1, whereinthe purge gas is selected from the group of helium (He), neon (Ne),argon (Ar), hydrogen (H₂), nitrogen (N₂), and combinations thereof. 7.The method of claim 1, wherein the nitrogen precursor contains acompound selected from the group consisting of nitrogen, ammonia,hydrazine, plasmas thereof, derivatives thereof and combinationsthereof.
 8. The method of claim 1, wherein the tantalum containingprecursor is selected from Ta(NMe₂)₅, Ta(NEt₂)₅, TBTDET tantalumhalides, pentakis(ethylmethylamino) tantalum (PEMAT),pentakis(diethylamino) tantalum (PDEAT), pentakis(dimethylamino)tantalum (PDMAT) and derivatives thereof.
 9. The method of claim 1,wherein the tantalum containing precursor is a tantalum basedorgano-metallic precursor.
 10. The method of claim 1, wherein thesubstrate is maintained at a pressure less than 100 Torr.
 11. The methodof claim 3, wherein the plasma annealing is performed with argon (Ar)and the argon (Ar) is flowed at a rate between 10 sccm to 2,000 sccm.12. The method of claim 1, wherein the substrate is maintained at apressure between 0.1 Torr to 50 Torr.
 13. A method of forming a tantalumnitride film, comprising: (a) chemisorbing tantalum from a tantalumcontaining precursor to form a layer of tantalum containing compound ona substrate, wherein the substrate is maintained at a temperaturebetween 20 degrees Celsius to 400 degrees Celsius; (b) stopping the flowof the tantalum containing precursor; (c) pulsing a purge gas to thesubstrate and stopping the flow of the purge gas to provide a pulse timeof less than about 1 second; (d) chemisorbing nitrogen from a nitrogencontaining precursor to a layer of nitrogen containing compound on thelayer of tantalum containing compound; (e) stopping the flow of thenitrogen containing precursor; (f) pulsing the purge gas to thesubstrate and stopping the flow of the purge gas to provide a pulse timeof less than about 1 second; and repeating (a)-(f) until a desiredthickness of the layers of tantalum containing compound and nitrogencontaining compound is reached.
 14. The method of claim 13, wherein thesubstrate is maintained at a temperature between 150 degrees Celsius to300 degrees Celsius.
 15. The method of claim 14, wherein the tantalumcontaining precursor is pentakis(ethylmethylamino) tantalum (PEMAT). 16.The method of claim 13, wherein chemisorbing tantalum from the tantalumcontaining precursor and chemisorbing nitrogen from the nitrogencontaining precursor forms multiple tantalum nitride sublayers on thesubstrate.
 17. The method of claim 13, wherein the tantalum containingprecursor is selected from Ta(NMe₂)₅, Ta(NEt₂)₅, TBTDET tantalumhalides, pentakis(ethylmethylamino) tantalum (PEMAT),pentakis(diethylamino) tantalum (PDEAT), pentakis(dimethylamino)tantalum (PDMAT) and derivatives thereof.
 18. The method of claim 13,wherein the purge gas is selected from the group of helium (He), neon(Ne), argon (Ar), hydrogen (H₂), nitrogen (N₂), and combinationsthereof.
 19. The method of claim 13, wherein the nitrogen precursorcontains a compound selected from the group consisting of nitrogen,ammonia, hydrazine, plasmas thereof, derivatives thereof andcombinations thereof.
 20. The method of claim 13, further comprising:plasma annealing the layers of tantalum containing compound and nitrogencontaining compound to remove nitrogen therefrom.